1. Field of the Invention
The present invention relates to a record player used for, e.g., a disc jockey (which will be simply referred to as DJ hereinafter), and more particularly to a record player suitable for a so-called scratch performance operation by which a phonograph record is directly rotated in forward and reverse directions to output sounds by fingering of an operator which is a kind of DJ performance pattern.
2. Description of the Prior Art
FIG. 1 is an operation explanatory drawing showing an operation state of a scratch performance using a conventionally known record player. A record player 1 has been conventionally used as means for reproducing information recorded on a phonograph record. In recent years, however, a scratch performance for creating artificial novel sound information through a cartridge 9 by directly artificially carrying out forward/reverse rotation of a phonograph record 3 with fingertips has been performed as a DJ performance pattern. In this case, the record player is used as means for mixing the sound information from the record player with the counterpart from other various attached sound sources to create a novel world of sound sources. That is, the record player 1 is used as if it is a single musical instrument.
FIGS. 2(A) and (B) are operation explanately drawings when using a prior art record player 1 for HiFi audio as such a scratch performance. FIG. 2(A) shows the operation when forwardly rotating a phonograph record 3 mounted on a turntable 2, and FIG. 2(B) illustrates the operation when inversely rotating the same. In these drawings, a direction of a needle pressure (stylus force) applied to a needlepoint 10 of each cartridge 9 is shown by a vector. Further, a tone arm 5 is made up of an arm shaft 6 and the cartridge 9.
Since the record player 1 which is widely used for DJ for the present has been essentially developed for the HiFi audio, it is designed in such a manner that the acousticity becomes optimum when used with the forward rotation in FIG. 2(A). Therefore, the arm shaft 6 of the tone arm 5 is held so as to be capable of swiveling in the horizontal direction by a vertical rotating shaft core (supporting point, rotating axis) P provided to a pivot portion 8 and the arm shaft 6 is curved in the form of S. That is, an offset angle xcex1 (it is generally 21.4xc2x0) is formed between an axial line direction 6xe2x80x2 of the arm shaft 6 and an axial direction 9xe2x80x2 of the cartridge 9 to inwardly bend the cartridge 9 so that a tracking error is compensated. Further, the arm shaft 6 is elongated to the side of the supporting point P and a needle pressure adjuster 7 is provided to the elongation so that reproduction is carried out with the optimum needle pressure.
In case of the DJ scratch performance, however, both a rotational speed number of revolutions and a direction of rotation arbitrarily vary as shown in FIGS. 2(A) and (B). At that time, the force applied to the needlepoint 10 of the cartridge 9 becomes a force F in the tangential direction in the forward rotation as shown in FIG. 2(A) while the same becomes a force Fxe2x80x2 in a tangential direction in the reverse direction as shown in FIG. 2(B). In regard to magnitudes of the respective forces F and Fxe2x80x2, these forces can be divided into component forces F2 and Fxe2x80x22 in the X-axis direction which are respectively straight lines connecting the supporting point P and the needlepoint 10 and the counterparts F1 and Fxe2x80x21 in the Y-axis direction which are vertical to the former forces.
In case of the forward rotation, a needle pressure F1 along the internal diameter direction of the phonograph record 3 is constantly applied to the needlepoint 10 during tracking as shown in FIG. 2(A). Further, in case of the reverse rotation, a needle pressure Fxe2x80x21 in the external diameter direction which is completely opposed to the former is applied. Therefore, when the phonograph record 3 is rotated in the forward/reverse direction in the scratch performance, the forces F1 and Fxe2x80x21 in the directions of the internal and external diameters are repeatedly applied to the needlepoint 10. When these forces F1 and Fxe2x80x21 become large and exceed a given frictional force to jut out from a record groove, the needlepoint 10 skips from the groove and a so-called xe2x80x9cneedle skip phenomenonxe2x80x9d occurs. In this case, a turbulence is generated in an output sound, which makes an audience uncomfortable.
Thus, despite of the recent increase in number of DJ performance wishers, the performance technique requiring the considerable skills is needed for changing between the forward rotation and the reverse rotation of the phonograph record 3 at high speed while preventing the needle skip from occurring. Accordingly, a number of performers is not increased in spite of a significant number of performance wishers. Naturally, this is also responsible for limiting pervasion of sound associated devices used together with the record player 1.
In view of the above-described problems, it is an object of the present invention to provide a record player which can avoid a needle skip phenomenon by suppressing inward and outward component forces applied to a needlepoint of a cartridge as possible when rapidly changing a rotating direction of a phonograph record to a forward direction and a reverse direction by a scratch performance operation and which can be satisfactorily used by an unskilled performer without being restricted to a practiced hand.
According to the present invention, the object can be attained by a record player for a disc jockey which can be adapted to a scratch performance operation for outputting a sound by directly rotating a phonograph record in forward and reverse directions by a finger operation of an operator, comprising: a turntable driven to rotate around a rotating shaft core C; an arm shaft which is supported so as to be capable of swiveling in a horizontal direction around a rotating shaft core P positioned outside the turntable and which is positioned on a straight line connecting the rotating shaft core P and a needle tracking a record groove of a phonograph record as viewed from a plane; and a cartridge which is held at a swiveling end of the arm shaft and detects a sound signal by the needle tracking the record groove of the phonograph record, the rotating shaft core P of the arm shaft being positioned on a straight line orthogonal to a straight line running through the rotating shaft core C of the turntable in the vicinity of the midpoint of an effective width a1a2 of the record groove.
According to the present invention, in order to suppress the needle skip caused when forwardly/inversely rotating the phonograph record by the finger operation, the positional relationship between the record groove on the turntable and the supporting point P of the arm shaft is defined so as to suppress inward and outward component forces applied to the needlepoint of the cartridge as possible. Therefore, three points, i.e., a start point R and an end point S of the record groove on a straight line B extending from the rotating shaft core C of the turntable in a radial pattern and a rotation center of a tone arm (rotating shaft core), namely, the supporting point P may form an isosceles triangle with the point P as an apex in a most preferable mode for embodying the present invention in theory. Further, when a straight line PQ connecting an intersection Q and the supporting point P is positioned on a straight line which extends through the intersection Q and is orthogonal to the straight line B or on a parallel line close to this straight line, the supporting point P may be arranged adjacent to or apart from the turntable.
A sliding sheet is intervened between the phonograph record and the turntable so that only the phonograph record can be inversely rotated by using fingertips while rotating the turntable in the forward direction with a fixed rotational speed. At this time, the phonograph record can be slid on the sliding sheet or the phonograph record and the sliding sheet can be slid on the turntable. It is to be noted that both the phonograph record and the turntable may be rotated in the reverse direction by using the fingertips.
When the rotating shaft core P of the arm shaft is positioned on a straight line which is orthogonal to the straight line B running through the rotating shaft core C of the turntable and which runs between points a3 and a4 for dividing the effective width a1a2 of the record groove into substantially quarters together with the intermediate point Q, the sufficient advantage can be obtained.
The rotating shaft core P of the arm shaft may be determined as follows. That is, the rotating shaft core P is determined on a straight line, which runs through the intersection Q of a first virtual circle W having a distance R0 from the rotating shaft core C of the turntable to the intermediate point Q of the effective width a1a2 as a radius and a second virtual circle D having a distance D0 between the respective rotating shaft cores C and P of the turntable and the arm shaft as a diameter, and which is orthogonal to the straight line B running through the rotating shaft core C of the turntable.
Most preferably, the start point R and the end point S of the record groove on the straight line B and the rotating shaft core P form an isosceles triangle with the rotating shaft core P as an apex. It is preferable that the rotating shaft core P is distanced away from the intersection Q as far as possible. In other words, the arm shaft is sufficiently lengthened. By doing so, the tracking error can be minimized at the start and end points R and S of the record groove. Extending the arm shaft toward the rotating shaft core P and providing a needle pressure adjuster on the extended portion can be favorable for adjusting the needle pressure.
In addition, when a horizontal rotating shaft core Pv allowing the arm shaft to rotate in the vertical direction is provided at a position above the top surface of the phonograph record, the needle pressure during the reverse rotation of the phonograph record can be larger than that during the forward rotation as will be described later, thereby further enhancing the efficacy for avoiding the needle skip during the reverse rotation. Incidentally, the needle pressure during the reverse rotation can be further increased as the distance from the needlepoint to the rotating shaft core Pv becomes smaller, namely, the length of the arm shaft becomes smaller. On the other hand, it is desirable to set the rotating shaft core P allowing the horizontal rotation away from the turntable as far as possible. In order to satisfy these requirements, S therefore, the horizontal rotating shaft core Pv allowing the vertical swiveling can be biased toward the cartridge away from the vertical rotating shaft core P allowing the horizontal swiveling.
Moreover, the needle pressure adjuster may be a dead weight whose center of gravity is positioned below the rotating shaft core Pv. In such a case, since both the needlepoint and (the center of gravity of) the dead weight provided on the both sides of the rotating shaft core Pv are positioned below the rotating shaft core Pv, a balance can be kept in the form of a needle thread take up (balancing toy). Therefore, although a side force applied to the needlepoint acts so as to oscillate the dead weight in the right-and-left direction (direction orthogonal to the arm shaft), this oscillation can be suppressed by a weight of the dead weight. Consequently, the side force generated to the needlepoint when changing the forward/reverse rotation can be suppressed, thereby further enhancing the effect for avoiding the needle skip.